C++ pointer comparison with []operator for arrays?

Question

I have been reading a book which says that accessing array elements by pointer arithmetic's is much faster than the [] operator. In short this code is faster than this code. The book does not say why. Is it advisible to use such pointer arithmetic's even if it provides significant improvement in speed?

#include <iostream>
using namespace std;

int main() {
    // your code goes here
    double *array = new double[1000000];
    for(int i = 0; i < 1000000; i++)
    {
        array[i] = 0;//slower?
    }
    delete[] array;
    return 0;
}

#include <iostream>
using namespace std;

int main() {
    // your code goes here
    double *array = new double[1000000];
    for(int i = 0; i < 1000000; i++)
    {
        *(array + i) = 0;//faster?
    }
    delete[] array;
    return 0;
}

EDIT:

Quote from book pg 369, 2nd last line

The pointer accessing method is much faster than array indexing.

Answer 1

No, they are exactly the same thing. I definitely suggest you to drop that book and pick another one up as soon as possible.

And even if there was any performance difference, the clarity of x[12] over *(x + 12) is much more important.

Answer 2

Array indices are just syntactic sugar for pointer arithmetic. Your compiler will boil down a[i] into *((a) + (i)). Agreed, run away from that book!

For more in-depth explanations, see

1. SO Answer
2. Eli Bendersky's explanation